[PATCH 03/16] mm: add vma_desc_size(), vma_desc_pages() helpers

[Lorenzo Stoakes]

It's useful to be able to determine the size of a VMA descriptor range used
on f_op->mmap_prepare, expressed both in bytes and pages, so add helpers
for both and update code that could make use of it to do so.

Signed-off-by: Lorenzo Stoakes <lorenzo.stoa...@oracle.com>
---
 fs/ntfs3/file.c    |  2 +-
 include/linux/mm.h | 10 ++++++++++
 mm/secretmem.c     |  2 +-
 3 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/fs/ntfs3/file.c b/fs/ntfs3/file.c
index c1ece707b195..86eb88f62714 100644
--- a/fs/ntfs3/file.c
+++ b/fs/ntfs3/file.c
@@ -304,7 +304,7 @@ static int ntfs_file_mmap_prepare(struct vm_area_desc *desc)
 
        if (rw) {
                u64 to = min_t(loff_t, i_size_read(inode),
-                              from + desc->end - desc->start);
+                              from + vma_desc_size(desc));
 
                if (is_sparsed(ni)) {
                        /* Allocate clusters for rw map. */
diff --git a/include/linux/mm.h b/include/linux/mm.h
index a6bfa46937a8..9d4508b20be3 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3560,6 +3560,16 @@ static inline unsigned long vma_pages(const struct 
vm_area_struct *vma)
        return (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 }
 
+static inline unsigned long vma_desc_size(struct vm_area_desc *desc)
+{
+       return desc->end - desc->start;
+}
+
+static inline unsigned long vma_desc_pages(struct vm_area_desc *desc)
+{
+       return vma_desc_size(desc) >> PAGE_SHIFT;
+}
+
 /* Look up the first VMA which exactly match the interval vm_start ... vm_end 
*/
 static inline struct vm_area_struct *find_exact_vma(struct mm_struct *mm,
                                unsigned long vm_start, unsigned long vm_end)
diff --git a/mm/secretmem.c b/mm/secretmem.c
index 60137305bc20..62066ddb1e9c 100644
--- a/mm/secretmem.c
+++ b/mm/secretmem.c
@@ -120,7 +120,7 @@ static int secretmem_release(struct inode *inode, struct 
file *file)
 
 static int secretmem_mmap_prepare(struct vm_area_desc *desc)
 {
-       const unsigned long len = desc->end - desc->start;
+       const unsigned long len = vma_desc_size(desc);
 
        if ((desc->vm_flags & (VM_SHARED | VM_MAYSHARE)) == 0)
                return -EINVAL;
-- 
2.51.0